Two years ago I bought an Asus laptop with Windows Vista pre-installed. I also received a recovery DVD with it. I now want to reinstall Windows and fully format the hard drive - however, the sticker with the Windows product key under the laptop is unreadable.

I tried recovering the key with ProduKey and similar software but they show another product key - it is different from the sticker's key (I checked on another Asus laptop and on my Dell laptop).

Is it possible to reinstall the operating system with the product key obtained from ProduKey? If not, how can I retrieve the product key? It seems stupid that it was only placed on the sticker that is destroyed after some time if you frequently hold the laptop on your lap.

The product key with Vista will differ because it uses an OEM licence key for the initial installation, which won't work when you reinstall. That's why there's a different key on the sticker, which is for you if you need to reinstall. Scott covers some of that in his answer about Dell.
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user3463Jun 23 '11 at 20:28

You don't need a key when using Recovery DVD's, it will install a key automatically and activate Vista for you.
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MoabJun 23 '11 at 20:35

In the end I was not able to recover the "real" key. However, I reinstalled windows from the asus recovery dvd and it didn't ask me for any keys.
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empiJul 19 '11 at 17:58

The reason why your keys are different is a fundamental difference between how OEM activation works and how normal activation works. When you get Windows pre-installed on your PC, it comes with special OEM activation files, which tell Windows to check for a certain code on the motherboard of the computer. If that code exists, then Windows knows that the computer was manufactured by that OEM, and verifies it against the activation file. If they match, then activation proceeds automatically. For these types of installations, one product key is used by essentially all of the computers that manufacturer installs that version of Windows on. The key on the sticker on the bottom of your laptop is essentially inactive, although it can be used if you lose the recovery media.

If you have the original recovery media, you can just install Windows with it, and it should automatically activate, as long as the recovery media is from that computer manufacturer. Windows should activate automatically when it connects to the internet. Do keep a record of the key you sniffed though, just in case activation fails. You can always call Microsoft to get free help with activation, if it does not work automatically.

Magical Jellybean Keyfinder is a free (as in beer) key retrieval tool that works with a wide variety of Microsoft products, including all their current operating systems office suites, as well as many other software packages. It is also extensible via definition files.

I recommend SIW. the trial version can decode the keys for all Microsoft products and quite a few others (with the trial you can't export the output, but copy and paste still works).

as for the key not being the same as what the tool shows.

From the website:

For those of you using this to retrieve serial numbers from a DELL, be aware that the key will be incorrect. DELL pre-activates all its versions of Windows with an identical serial and places the license key on the outside of your case. This saves them money because it's much more efficient for these large companies to install Windows once and then clone the drive.